Frequent bad breath may be caused by poor oral hygiene or by disorders of the gastrointestinal digestive system. Frequent bad breath, also known as bad oral odor, can seriously affect normal social life and life. The common cause of bad breath is poor oral hygiene, after eating without timely removal, food residues accumulate around the teeth, bacteria use food as a substrate fermentation acid production, the appearance of corrosive odor, that is, bad breath. Gingivitis can also develop over time, and this condition requires dental scaling to improve. Frequent bad breath may also be caused by tooth decay, tooth decay is not treated in time, bacteria further infect the tooth nerve, resulting in pulp tissue septic necrosis, the unique odor of dead pulp teeth. Pulp necrosis requires root canal treatment to relieve the odor. Frequent bad breath may also be caused by imperfect digestive system of the gastrointestinal tract, eating meat or protein and legumes, which are not completely decomposed and have a special odor of decay, which can also cause bad breath, and this situation needs to be examined accordingly. So often bad breath may be caused by gingivitis, or necrosis of the dental nerve, or may be caused by imperfect digestion of the gastrointestinal tract.